The present invention relates generally to systems for depositing a material onto a surface, and more particularly, to control systems for metering the amount of material being dispensed.
Materials are often applied over surfaces using a fluid dispensing system. Generally, the fluid dispensing system includes a reservoir, a material delivery system, an application apparatus, and a control system. The reservoir stores the material. The material may include a wide variety of materials such as paints, ultraviolet (UV) acrylic gels, moisture and thermal cure silicones, and the like. The material delivery system delivers the material from the reservoir to the application apparatus. The material delivery system may include conduits for carrying the material and a control valve to control the flow of material. The application apparatus may include a spraying and/or dispensing device, and a positioning apparatus, such as a multi-degree of freedom robotic positioning apparatus. The spraying or dispensing devices are commonly attached to the positioning apparatus, which provides accurate positional displacement relative to an article in which the material is being applied.
There are two basic methods of applying materials to surfaces. These include beads of material applied to specific locations on the article, and substantially uniform thickness coatings applied over large sections of the article. For most articles, the materials are typically applied using devices such as spray guns, spray nozzles, or dispensing nozzles. For spraying, such devices generally include a pressurized liquid material that is atomized by compressed gas and is then directed toward the surface to be coated. For dispensing, such devices generally include a pressurized liquid material that is dispensed through a nozzle tip in close proximity to the surface being coated.
Generally, the liquid material is applied during a fixed period of time. Unfortunately, changes in the viscosity of the liquid material may cause a change in the amount of liquid material that is applied to the surface during the fixed period of time. Temperature changes of the liquid material may produce a change in the liquid material viscosity. Commonly, ambient temperature changes occur in a production area, causing the viscosity of the liquid material to change. Also, changes in the pressure of the liquid material may result in a change in the amount of liquid material delivered during the fixed period of time. Additionally, some materials will change viscosity when subject to flow. Furthermore, a time-consuming manual adjustment of a control valve mounted on each spraying or dispensing apparatus is often necessary when these changes occur.
In order to overcome the above deficiencies, the present invention provides an active compensation metering system. The active compensation metering system automatically compensates for material changes due to changes in material pressure, material temperature, and material viscosity. A computerized controller included in the active compensation metering system can turn a plurality of spraying or dispensing valves on or off. Additionally, the active compensation metering system eliminates the necessity for an operator to manually adjust a control valve on the spraying or dispensing valve during a production cycle.
The present invention generally provides an apparatus comprising:
a reservoir containing a material;
an application apparatus for applying the material onto a surface;
a material control valve apparatus for regulating a volume of the material flowing from the reservoir to the application apparatus;
a flow measuring device for measuring the volume of the material flowing from the reservoir to the application apparatus; and
a controller coupled to the flow measuring device for calculating a volume flow rate during a first interval of time, and for adjusting the material control valve to obtain a predetermined volume flow rate during a second interval of time.